Problem: Solve for $x$ : $30 = x - 19$
Explanation: Add $19$ to both sides: $ \begin{eqnarray} \\ \hphantom{30 {+ 19}} &\hphantom{=}& \hphantom{x} \\ 30 &=& x - 19 \\ \\ {+19} && {+19} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 30 {+ 19} &=& x \\ \end{eqnarray} $ Simplify. $ x = 49$